Linear alkylbenzenes (LAB) are compounds that have significant commercial importance. Linear alkylbenzene sulfonate (LAS) compounds made by sulfonation of linear alkylbenzene are used in the manufacture of detergents and other products. Because linear alkylbenzenes are more easily biodegradable than branched alkylbenzenes, linear alkylbenzenes have essentially replaced branched alkylbenzenes in detergents and other products. In particular, linear alkylbenzenes with long alkyl chains, such as chains having about 10 to about 14 carbons, are commonly used. However, linear alkylbenzenes with longer chains and with shorter chains also are commercially important.
Linear alkylbenzenes often are made by alkylation of benzene with olefins. Positional isomers, such as 2-phenyl, 3-phenyl, 4-phenyl, 5-phenyl, and the like, result from this alkylation of benzene with long chain olefins. The distribution of the phenyl along the alkyl chain produces different products.
Historically, linear alkylbenzenes have been manufactured commercially using Friedel-Crafts condensation employing catalysts such as aluminum chloride, or by using strong acid catalysts such as hydrogen fluoride, for example, to alkylate benzene with olefins. In 1995, a solid bed alkylation process, the Detal™ process, using a solid non-corrosive acid catalyst was introduced.
Linear alkylbenzenes with a high percentage of the 2-phenyl isomer are highly desired because, when sulfonated, such compounds have long tails that provide enhanced solubility and detergent properties.
The 2-phenyl isomer content of the product is process dependent. Solid alkylation catalysts, such as those used in the Detal™ process, produce products with 2-phenyl isomer content between 25 and 35 percent. HF-catalyzed processes typically yield a 2-phenyl isomer content less than 20 percent, and AlCl3 typically yield between 30 and 33 percent. The properties of linear alkylbenzenes and linear alkylbenzene sulfonate produced from these three processes have been disclosed by Berna and coworkers in the following publications. Journal of Surfactants and Detergents, Vol. 3, No. 2 (July 2000) pages 353 through 359, JAOCS, Vol. 72, No. 1 (1995) pages 115 through 122, and Tenside Surfactants Detergents 25 (1988) 4, pages 216 through 221.
Current LAB manufacturing processes employing solid alkylation catalysts use kerosene-based C9 to C16 material from a Pacol™ dehydrogenation process, which is typically a mixture of about 9-15% olefins in paraffin.
Gas-to-liquid (GTL) technologies for the generation of C9 to C16 range of hydrocarbons have raised interest in the possibility of producing LAB using a GTL-based feed source. The ability to use a GTL feedstock would reduce dependence on crude-based feedstocks.
Thus, there exists a need for additional methods for making linear alkylaromatics by alkylating aromatic compounds with olefins.